1. Field of the Invention
The present invention relates to a mobile terminal capable of receiving digital TV broadcast, and more particularly, to a mobile terminal breaking a phase-noise signal caused by a high power transmission signal of a mobile phone such as GSM when receiving digital TV broadcasting such as DVB-H, preventing deterioration of sensitivity of receiving of digital TV broadcast, which is caused by a phase-noise signal of a high power GSM signal, and improving reception performance of digital TV broadcasting such as DVB-H and mass productivity and a method of reducing interfering phase-noise.
2. Description of the Related Art
In general, recently there has been a lot of interest in digital TV broadcasting and therefore technologies have been developed, such as digital multimedia broadcasting (DMB) in Korea and digital video broadcasting (DVB) in Europe.
In DMB, there are terrestrial DMB and satellite. In DVB, there are DVB-T receiving broadcast from general broadcasting companies by a fixed device for home or office and DVB-H capable of using low power and having mobility and portability for a mobile phone or portable video device.
As mobile terminals corresponding to mobile communication terminals such as mobile phones and PDAs have been composed, a mobile phone including DVB-H will come out. In this case, when one terminal supports two or more functions such as GSM, GPRS and DVB-H, receiving sensitivity of each module is deteriorated by mutual interference. Accordingly, there is required proper solution for the deterioration of receiving sensitivity of each module, which is caused by the mutual interference.
FIG. 1 is a configuration diagram illustrating a conventional GSM mobile phone including a DVB-H receiver. Referring to FIG. 1, the conventional GSM mobile phone includes a GSM transmitter/receiver 11 transmitting and receiving a GSM signal of approximately 900 MHz in which TX corresponds to 880 to 915 MHz and RX corresponds to 925 to 960 MHz and a DVB-H receiver 12 receiving a DVB-H broadcasting signal having a band of approximately 470 to 750 MHz.
In FIGS. 2A and 2B, there are illustrated effects of phase-noise of a GSM900 transmission band corresponding to approximately 900 MHz for a DVB-H reception band in a conventional mobile terminal.
FIGS. 2A and 2B are diagrams illustrating a of phase-noise effect of a GSM900 transmission band for a DVB-H reception band. Referring to FIG. 2A, there is illustrated a phase-noise effect of the GSM900 transmission band for the DVB-H reception band when there is not included a band pass filter removing the GSM900 transmission band in an input port of the DVB-H receiver 12. Referring to FIG. 2B, there is illustrated a phase-noise effect of the GSM900 transmission band for the DVB-H reception band when there is included the band pass filter in the input port of the DVB-H receiver 12.
Referring to FIG. 2A, the DVB-H band corresponds to approximately 470 to 750 MHz and the GSM900 transmission band corresponds to approximately 880 to 915 MHz. In FIGS. 2A and 2B, a phase-noise signal of a GSM transmission signal flows into the DVB-H reception band and has a bad effect on a DVB-H reception signal.
On the other hand, in conventional mobile terminal, while receiving digital broadcasting via the DVB-H receiver 12, GSM transmission/reception may be performed via the GSM transmitter/receiver 11. Also, while receiving digital broadcasting via the DVB-H receiver 12, the GSM transmission/reception may be performed via another near GSM transmitter/receiver.
Referring to FIG. 2B, since power of the GSM transmission signal is amplified high to approximately 33 dBm via a built-in power amplifier in the GSM transmitter/receiver 11, the GSM transmission signal of high power may flow into the DVB-H receiver 12 via an antenna. In this case, since the GSM transmission signal acts as noise to the DVB-H broadcasting signal, a band pass filter (BPF) may be included in the input port of the DVB-H receiver 12 in order to reduce the noise. The BPF allows a DVB-H reception signal of approximately 470 to 750 MHz to pass and breaks a GSM transmission signal more than 880 MHz.
The BPF included in the DVB-H receiver 12 of the conventional GSM mobile phone may improve noise caused by intermodulation between the GSM transmission signal and a DVB-T signal, generated in an RF circuit of the DVB-H receiver 12, by breaking the GSM transmission signal.
However, in the conventional GSM mobile phone, though including the BPF, a phase-noise component of a GSM transmission signal in a band of 470 to 750 MHz is not broken, passes the BPF without reduction, and has a bad effect on the DVB-H reception band to deteriorate receiving sensitivity of the DVB-H broadcasting.
FIG. 3 is a measurement graph illustrating receiving sensitivity of DVB-H against phase-noise in a conventional GSM mobile terminal. Referring to FIG. 3, when a GSM transmission signal flows into the DVB-H receiver 12 via a second antenna ANT2 and phase-noise of the GSM transmission signal has a bad effect on a DVB-H reception band, deterioration of the receiving sensitivity of DVB-H is illustrated according to a level of the phase-noise of the GSM transmission signal.
Referring to FIG. 3, when the level of the phase-noise of the GSM transmission signal flowing via the second antenna ANT2 corresponds to −150 dBm/Hz, the receiving sensitivity of the DVB-H receiver 12 is deteriorated by −24 dB from −93.5 dBm G11 when there is no GSM phase-noise, to −69.5 dBm G12.
Namely, since the reduction of the GSM transmission signal is not high when using the BPF, the conventional GSM mobile phone has a problem of the deterioration of the receiving sensitivity of the DVB-H broadcasting, caused by flow of a transmission signal into the DVB-H receiver 12 as noise.